Methods, systems, and computer readable media for adaptively calibrating test systems for different interconnects

ABSTRACT

The subject matter described herein relates to methods, systems, and computer readable media for adaptive calibration of test systems to interconnects. In some examples, a control circuit performs a method for adaptive calibration including determining, for each configurable calibration parameter of a number of configurable calibration parameters for a receiver for processing a received signal from an interconnect coupled to the receiver, a range of valid values for the configurable calibration parameter. The method further includes for each configurable calibration parameter: sweeping the configurable calibration parameter across a subset of values from the range of valid values for the configurable calibration parameter; and testing the received signal from the interconnect for each value in the subset of values and storing a result of the testing for the value. The method further includes determining a set of calibrated values for the configurable calibration parameters based on the results of the testing.

TECHNICAL FIELD

The subject matter described herein relates generally to communicationstest systems. More particularly, the subject matter described hereinrelates to methods, systems, and computer readable media for adaptivecalibration of test systems for different interconnects.

BACKGROUND

Interconnects include cables, both electrical and optical, used toconnect test systems to systems under test. Often, a test system iscalibrated for a particular interconnect or family of interconnects. Asa result, manual calibration can be required if the test system is usedwith interconnects other than those for which the test system iscalibrated.

The quality of calibration of a test system to an interconnect can bemeasured using an eye diagram, which can be generated using anoscilloscope. An oscilloscope is a type of electronic test instrumentthat allows observation of constantly varying signal voltages. Forexample, an oscilloscope can present a two-dimensional plot of one ormore signals as a function of time. Oscilloscopes can be used incommunications test systems to display an eye diagram of a digitalsignal output from a receiver. The digital signal is repetitivelysampled and applied to a vertical input of the oscilloscope and the datarate triggers the horizontal sweep, resulting in a superposition of manypossible realizations of the signal viewed on top of each other. A userof a communications test system can use the eye diagram to evaluate thecombined effects of noise and interference on the signal.

The user can also calibrate the receiver to a particular interconnect byadjusting the receiver and observing the effects of adjustments on theeye diagram. The user changes one parameter value, looks at the eye,then changes another parameter value, and so on. The user may have totest a hundred or more different configurations. Calibrating a receiverin this manner can result in an optimal setting but takes a long timeand requires an oscilloscope and a certain amount of skill on the partof the user.

In light of these difficulties, there exists a need for methods,systems, and computer readable media for adaptive calibration of testsystems for different interconnects.

SUMMARY

The subject matter described herein relates to methods, systems, andcomputer readable media for adaptive calibration of test systems tointerconnects. In some examples, a control circuit performs a method foradaptive calibration including determining, for each configurablecalibration parameter of a number of configurable calibration parametersfor a receiver for processing a received signal from an interconnectcoupled to the receiver, a range of valid values for the configurablecalibration parameter. The method further includes for each configurablecalibration parameter: sweeping the configurable calibration parameteracross a subset of values from the range of valid values for theconfigurable calibration parameter; and testing the received signal fromthe interconnect for each value in the subset of values and storing aresult of the testing for the value. The method further includesdetermining a set of calibrated values for the configurable calibrationparameters based on the results of the testing.

The subject matter described herein can be implemented in software incombination with hardware and/or firmware. For example, the subjectmatter described herein can be implemented in software executed by aprocessor. In one exemplary implementation, the subject matter describedherein can be implemented using a non-transitory computer readablemedium having stored thereon computer executable instructions that whenexecuted by the processor of a computer control the computer to performsteps. Exemplary computer readable media suitable for implementing thesubject matter described herein include non-transitory computer-readablemedia, such as disk memory devices, chip memory devices, programmablelogic devices, and application specific integrated circuits. Inaddition, a computer readable medium that implements the subject matterdescribed herein may be located on a single device or computing platformor may be distributed across multiple devices or computing platforms.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example communications environmentincluding a test system;

FIG. 2 is a block diagram of an example control circuit for adaptivecalibration of the test system;

FIG. 3 is a diagram illustrating an example multi-dimensional array oftest results as an object;

FIG. 4A is a block diagram of an example transmitter;

FIG. 4B is a block diagram of an example receiver;

FIG. 4C is a block diagram of an example equalizer; and

FIG. 5 is a flow diagram of an example method for adaptive calibrationof a test system.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an example communications environment 100including a test system 102 configured for communication over aninterconnect 104 and one or more optional devices under test (DUTs) 106.Test system 102 may be a physical device that sends test traffic and/orsignals to DUTs 106 and that monitors the response of DUTs 106.

Interconnect 104 can include any appropriate medium or device or bothfor carrying a communications signal. For example, interconnect 104 canbe a fiber-optic cable, a copper wire cable, or a radio link includingwireless transmitters and receivers or transceivers. Interconnect 104can include elements such as patch panels, couplers, and taps. DUTs 106can include any appropriate devices that it is desirable to test; forexample, DUTs 106 can include routers, switches, servers, firewalls,network address translators (NATs), amplifiers, and repeaters.

Test system 102 includes a transmitter 108 for transmitting thecommunications signal to interconnect 104. Test system 102 also includesa receiver 110 for receiving a return signal from interconnect 104 orDUTs 106. Test system 102 is configured to analyze the return signal tocharacterize interconnect 104. Test system 102 can calibrate thetransmitter 108 or the receiver 110 or both to compensate for noise andinterference introduced by interconnect 104.

Test system 102 includes a tester 112 including a generator 114 and acomparator 116. Generator 114 is a device configured to generate a testsignal. For example, generator 114 can generate a pseudo-random bitsequence. Comparator 116 is a device configured to compare the returnsignal to the test signal, e.g., to characterize noise and interferenceintroduced by interconnect 104. For example, where the test signal is adigital signal, comparator 116 can perform a bit-by-bit comparisonbetween the test signal and the return signal.

Test system 102 includes a control circuit 118. Control circuit 118 isconfigured to perform adaptive calibration of test system 102 tointerconnect 104. Control circuit 118 can be implemented in anyappropriate combination of hardware, software, and firmware. Forexample, control circuit 118 can be implemented as a system of one ormore computers configured, by virtue of appropriate programming, tocontrol transmitter 108, receiver 110, and tester 112.

In operation, control circuit 118 determines, for each configurablecalibration parameter for transmitter 108 or receiver 110 or both, arange of valid values for the configurable calibration parameter. Foreach configurable calibration parameter, control circuit 118 sweeps theconfigurable calibration parameter across a subset of values for therange of valid values for the configurable calibration parameter.Control circuit 118 tests, using tester 112, the received signal frominterconnect 104 for each value in the subset of values and stores aresult of the testing for the value. Control circuit 118 determines aset of calibrated values for the configurable calibration parametersbased on the results of the testing.

Test system 102 can include an optional oscilloscope 120. A user of testsystem 102 can use oscilloscope 120 to validate the set of calibratedvalues produced by control circuit 118, e.g., by looking at an eyediagram produced using the set of calibrated values. The user may alsowish to further customize the set of calibrated values usingoscilloscope 120. In some examples, test system 102 lacks oscilloscope120, which can reduce technical requirements for test system 102, e.g.,size, weight, and cost requirements for test system 102.

In some examples, test system 102 includes a display and a user inputdevice. A user of test system 102 can connect interconnect 104 to testsystem 102 and then use the user input device to initiate adaptivecalibration by control circuit 118 and use the display to observe statusindicators and the determined set of calibrated values. In someexamples, test system 102 is programmed to perform various other testfunctions, and the user can use the display and the user input device toconfigure and perform the other test functions in addition to theadaptive calibration function.

FIG. 2 is a block diagram of an example control circuit 118 for adaptivecalibration of the test system. Control circuit 118 includes variousmodules including a parameter range determiner 202, a parameter sweeper204, an error rate determiner 206, and a parameter calibrator 208. Themodules can be implemented in any appropriate combination of hardware,firmware, and software.

Parameter range determiner 202 is configured to determine, for eachconfigurable calibration parameter for a receiver or transmitter orboth, a range of valid values for the configurable calibrationparameter. For example, suppose that the receiver includes an equalizer.The configurable calibration parameters can be equalization parametersof the equalizer. If the equalizer includes a multi-tap filter, then atleast some of the configurable calibration parameters can be weightingvalues for the taps of the multi-tap filter. Determining the validranges can include, e.g., reading the valid ranges from memory on thereceiver, prompting a user to enter the valid ranges using a display anda user input device, or downloading the valid ranges from a server overa data communications network.

Parameter sweeper 204 is configured to sweep the configurablecalibration parameters for testing. For each configurable calibrationparameter, parameter sweeper 204 sweeps the configurable calibrationparameter across a subset of values from the range of valid values forthe configurable calibration parameter. For example, parameter sweeper204 can select a configurable calibration parameter, fix the values ofthe other unselected configurable calibration parameters, and sweep theselected configurable calibration parameter across the subset of valueswhile holding constant the fixed values of the other unselectedconfigurable calibration parameters. Parameter sweeper 204 can changethe value of a configurable calibration parameter, for example, byoutputting a control signal or writing a value to an appropriateregister or other location in memory of a transmitter or receiver.

Error rate determiner 206 is configured to test the received signal fromthe interconnect for each value in the subset of values, determines anerror rate for the value, and stores the error rate as a result of thetesting for the value. For example, error rate determiner 206 can usethe tester 112 of FIG. 1 to perform the testing. Testing the receivedsignal can include supplying, by a transmitter, a known signal to theinterconnect and determining an error rate by comparing a processedreceive signal from the receiver to the known signal. For example, errorrate determiner 206 can determine a bit error rate using a pseudo-randombit sequence by dividing the number of bits resolved in error by thetotal number of bits in the pseudo-random bit sequence.

In some examples, parameter sweeper 204 sweeps the configurablecalibration parameter across the subset of values by sweeping theconfigurable calibration parameter through selected values from therange of valid values for the configurable calibration parameter untilan end condition is reached based on the results of the testing. Forexample, the end condition can be reached when an error rate resultingfrom the testing is below a threshold error rate, e.g., when the errorrate drops to zero for pseudo-random bit sequence of sufficient length.

In some examples, parameter sweeper 204 initializes the configurablecalibration parameter to a first value and then increases theconfigurable calibration parameter until an end condition is reachedbased on the results of the testing. Then, parameter sweeper 204initializes the configurable calibration parameter to a second valuegreater than the first value and decreases the configurable calibrationparameter until the end condition is reached. In this manner, parametersweeper 204 probes the range of values inwards from a low value and ahigh value in search of a middle range of values that produce testingresults deemed acceptable.

In general, parameter sweeper 204 sweeps the configurable calibrationparameters through a subset of values from the range of valid values andnot the entire range of valid values. For example, parameter sweeper 204can step through values by incrementing or decrementing at fixed orrandom intervals or using a binary search algorithm or any appropriatealgorithm for sampling the range of valid values. By avoiding the entirerange of valid values, parameter sweeper 204 can identify ranges ofvalues that produce acceptable testing results in less time than acomplete brute force search would require. The resulting reduction intime means that control circuit 118 can be used to calibrate testsystems to interconnects without requiring a system engineer tocharacterize those interconnects before installation.

Parameter calibrator 208 is configured to determine a set of calibratedvalues for the configurable calibration parameters based on the resultsof the testing. For example, parameter calibrator 208 can determine acentroid of a multi-dimensional array formed by the results of thetesting. Such a multi-dimensional array is formed by viewing eachconfigurable calibration parameter as a dimension and the test resultsfrom sweeping that configurable calibration parameter as data pointsalong that dimension.

Since the testing reveals middle ranges of values presumed to produceacceptable testing results, determining the centroid of themulti-dimensional array will ordinarily result in the set of calibrationvalues being close to an optimal set of calibration values or at least aset of calibration values that produce testing results deemedacceptable.

FIG. 3 is a diagram illustrating an example multi-dimensional array oftest results as an object 300. For purposes of illustration, supposethat the test system 102 of FIG. 1 is calibrating three configurablecalibration parameters of the receiver 110 of FIG. 1. In one example,the three configurable calibration parameters can be, e.g., pre, post,and main tap values of an equalizer used in receiver 110.

The three configurable calibration parameters can be visualized as athree-dimensional set of axis 302. The result of sweeping oneconfigurable calibration parameter, on the x-axis, while holding theother two configurable calibration parameters constant, on the y and zaxes, results in a row 304 of test results. Row 304 includes a middlerange 306 of results where the results were deemed acceptable, i.e.,where the error rate of testing at those configurable calibrationparameters was below the threshold. Not all of the values in middlerange 306 need to have been actually tested—test system 102 may havestopped sweeping the configurable calibration test parameter as soon asacceptable results were achieved in going from left to right and thenright to left (or in the reverse order).

Although only one row is illustrated, the result of collectivelysweeping through the three configurable calibration parameters wouldfill object 300 with rows of results. Determining the centroid of themulti-dimensional array is then accomplished by considering thelocations in space with positive results as having mass and thelocations in space without positive results as not having mass. Anyappropriate algorithm can be used to determine the centroid. The valuesof the configurable calibration parameters at the centroid can beselected as the calibrated set of configurable calibration parameters.

FIG. 4A is a block diagram of an example transmitter 108. Transmitter108 includes an equalizer 402, a clock generator 406, and memory 408.Equalizer 402 can be configured, for example, to pre-distort transmittedpulses in order to invert channel distortion, e.g., at the cost ofattenuated transmit signal. Equalizer 402 can include a multi-tap filter404, e.g., a finite impulse response (FIR) filter. Each tap has arespective weight, and the weights of the taps can be calibrated by thecontrol circuit 118 of FIG. 1.

Clock generator 406 is configured to generate a clock signal for use bytransmitter 108. Clock generator 406 may also have configurablecalibration parameters that can be calibrated by the control circuit 118of FIG. 1. Memory 408 can store valid ranges of the configurablecalibration parameters for equalizer 402 or clock generator 406 or both.In some examples, control circuit 118 reads memory 408 to determinevalid ranges of the configurable calibration parameters.

FIG. 4B is a block diagram of an example receiver 110. Receiver 110includes an equalizer 410, a clock recovery circuit 414, and memory 416.Equalizer 410 can be, for example, a decision feedback equalizer.Equalizer 410 can include a multi-tap filter 412, e.g., a finite impulseresponse (FIR) filter. Each tap has a respective weight, and the weightsof the taps can be calibrated by the control circuit 118 of FIG. 1.

Clock recovery circuit 414 is configured to recover a clock signal froma received signal. Clock recovery circuit 414 may also have configurablecalibration parameters that can be calibrated by the control circuit 118of FIG. 1. Memory 416 can store valid ranges of the configurablecalibration parameters for equalizer 410 or clock recovery circuit 414or both. In some examples, control circuit 118 reads memory 416 todetermine valid ranges of the configurable calibration parameters.

FIG. 4C is a block diagram of an example equalizer 410. In theillustrated example, equalizer 410 is a non-linear decision feedbackequalizer. Equalizer 410 receives an incoming signal 450 and sumsincoming signal 450 with a feedback signal at a feedback summer 456. Aslicer 454 makes a symbol decision based on the output of feedbacksummer 456, i.e., slicer 454 quantizes its input, resulting in an outputsignal 452. Output signal 452 is fed into multi-tap filter 412, whichincludes a number of delay elements. Each delayed output is multipliedby a weight and summed at a filter summer 458 coupled to feedback summer456. In operation, filter summer 458 subtracts inter-symbol interferencefrom incoming signal 450 using multi-tap filter 412 to result in acleaner output signal 452.

FIG. 5 is a flow diagram of an example method 500 for adaptivecalibration of a test system. Method 500 can be performed by a controlcircuit, e.g., the control circuit 118 of FIG. 1, and for purposes ofillustration, method 500 will be described with respect to a controlcircuit that performs method 500. The control circuit can be a system ofone or more computers configured to perform method 500 by virtue ofappropriate programming.

The control circuit determines, for each configurable calibrationparameter of a number of configurable calibration parameters for areceiver for processing a received signal from an interconnect coupledto the receiver, a range of valid values for the configurablecalibration parameter (502). For example, the receiver can include anequalizer, and the configurable calibration parameters can beequalization parameters. In some examples, the equalizer includes amulti-tap filter and the configurable calibration parameters areweighting values for the taps of the multi-tap filter. As anotherexample, the configurable calibration parameters can specify anamplitude/gain in the system.

The control circuit fixes parameter values for all of the configurablecalibration parameters except for one configurable calibration parameterto sweep (504). The control circuit sweeps the one configurablecalibration parameter across a subset of values from the range of validvalues for that configurable calibration parameter (506).

Sweeping the configurable calibration parameter can include holding eachof the other configurable calibration parameters constant at the fixedvalues while sweeping the configurable calibration parameter. Forexample, sweeping the configurable calibration parameter across thesubset of values can include sweeping the configurable calibrationparameter through selected values from the range of valid values for theconfigurable calibration parameter until an end condition is reachedbased on the results of the testing. The end condition can be reached,e.g., when an error rate resulting from the testing is below a thresholderror rate.

In some examples, sweeping the configurable calibration parameter acrossthe subset of values includes initializing the configurable calibrationparameter to a first value and then increasing the configurablecalibration parameter until an end condition is reached based on theresults of the testing. Then, the control circuit initializes theconfigurable calibration parameter to a second value greater than thefirst value and decreases the configurable calibration parameter untilthe end condition is reached.

The control circuit tests the received signal from the interconnect foreach value while sweeping the configurable calibration parameter acrossthe subset of values from the range of valid values for thatconfigurable calibration parameter and stores a result of the testingfor the value (508). Testing the received signal from the interconnectcan include supplying, by a transmitter, a known signal to theinterconnect and determining an error rate by comparing a processedreceive signal from the receiver to the known signal. For example, theknown signal can be a pseudo-random bit sequence, and determining theerror rate can include determining a bit error rate using thepseudo-random bit sequence.

The control circuit determines whether there are more parameters tosweep (510). If so, the control circuit returns to fix parameter values(504), sweep another parameter (506), and record the results of testingduring the sweep (508). If not, then the control circuit determineswhether a valid set of calibrated values was found (512), e.g., whetherthe error rate ever dropped below or above the threshold error rateduring sweeping. If yes, then the control circuit determines a set ofcalibrated values for the configurable calibration parameters based onthe results of the testing (514). For example, determining the set ofcalibrated values for the configurable calibration parameters based onthe results of the testing can include determining a centroid of amulti-dimensional array formed by the results of the testing. If not,then the control circuit provides an indication that calibratedparameter values were not found (516), e.g., the control circuit causesa message to be displayed on a display screen or turns on an errorlight.

Accordingly, while the methods, systems, and computer readable mediahave been described herein in reference to specific embodiments,features, and illustrative embodiments, it will be appreciated that theutility of the subject matter is not thus limited, but rather extends toand encompasses numerous other variations, modifications and alternativeembodiments, as will suggest themselves to those of ordinary skill inthe field of the present subject matter, based on the disclosure herein.

Various combinations and sub-combinations of the structures and featuresdescribed herein are contemplated and will be apparent to a skilledperson having knowledge of this disclosure. Any of the various featuresand elements as disclosed herein may be combined with one or more otherdisclosed features and elements unless indicated to the contrary herein.Correspondingly, the subject matter as hereinafter claimed is intendedto be broadly construed and interpreted, as including all suchvariations, modifications and alternative embodiments, within its scopeand including equivalents of the claims.

It is understood that various details of the presently disclosed subjectmatter may be changed without departing from the scope of the presentlydisclosed subject matter. Furthermore, the foregoing description is forthe purpose of illustration only, and not for the purpose of limitation.

What is claimed is:
 1. A system for calibrating a receiver for aninterconnect, the system comprising: a receiver for processing areceived signal from an interconnect, wherein the receiver is configuredto process the signal using a plurality of configurable calibrationparameters each having a range of valid values; and a control circuitconfigured to calibrate the configurable calibration parameters to theinterconnect by performing operations comprising: for each configurablecalibration parameter: sweeping the configurable calibration parameteracross a subset of values from the range of valid values for theconfigurable calibration parameter; and testing the received signal fromthe interconnect for each value in the subset of values and storing aresult of the testing for the value; and determining a set of calibratedvalues for the configurable calibration parameters based on the resultsof the testing.
 2. The system of claim 1, wherein sweeping theconfigurable calibration parameter comprises holding each of theconfigurable calibration parameters, other than the configurablecalibration parameter, constant while sweeping the configurablecalibration parameter.
 3. The system of claim 1, comprising atransmitter, wherein testing the received signal from the interconnectcomprises supplying, by the transmitter, a known signal to theinterconnect and determining an error rate by comparing a processedreceive signal from the receiver to the known signal.
 4. The system ofclaim 3, wherein supplying the known signal comprises supplying apseudo-random bit sequence and wherein determining the error ratecomprises determining a bit error rate using the pseudo-random bitsequence.
 5. The system of claim 1, wherein sweeping the configurablecalibration parameter across the subset of values comprises sweeping theconfigurable calibration parameter through selected values from therange of valid values for the configurable calibration parameter untilan end condition is reached based on the results of the testing.
 6. Thesystem of claim 5, wherein the end condition is reached when an errorrate resulting from the testing is below or above a threshold errorrate.
 7. The system of claim 1, wherein sweeping the configurablecalibration parameter across the subset of values comprises:initializing the configurable calibration parameter to a first value andthen increasing the configurable calibration parameter until an endcondition is reached based on the results of the testing; andinitializing the configurable calibration parameter to a second valuegreater than the first value and then decreasing the configurablecalibration parameter until the end condition is reached.
 8. The systemof claim 1, wherein determining the set of calibrated values for theconfigurable calibration parameters based on the results of the testingcomprises determining a centroid of a multi-dimensional array formed bythe results of the testing.
 9. The system of claim 1, wherein thereceiver comprises an equalizer and wherein at least some of theconfigurable calibration parameters comprises equalization parameters.10. The system of claim 9, wherein the equalizer comprises a multi-tapfilter and the at least some of the configurable calibration parameterscomprises weighting values for the taps of the multi-tap filter.
 11. Amethod for adaptively calibrating a test system for an interconnect, themethod comprising: determining, by a control circuit, for eachconfigurable calibration parameter of a plurality of configurablecalibration parameters for a receiver for processing a received signalfrom an interconnect coupled to the receiver, a range of valid valuesfor the configurable calibration parameter; for each configurablecalibration parameter: sweeping the configurable calibration parameteracross a subset of values from the range of valid values for theconfigurable calibration parameter; and testing the received signal fromthe interconnect for each value in the subset of values and storing aresult of the testing for the value; and determining a set of calibratedvalues for the configurable calibration parameters based on the resultsof the testing.
 12. The method of claim 11, wherein sweeping theconfigurable calibration parameter comprises holding each of theconfigurable calibration parameters, other than the configurablecalibration parameter, constant while sweeping the configurablecalibration parameter.
 13. The method of claim 11, wherein testing thereceived signal from the interconnect comprises supplying, by atransmitter, a known signal to the interconnect and determining an errorrate by comparing a processed receive signal from the receiver to theknown signal.
 14. The method of claim 13, wherein supplying the knownsignal comprises supplying a pseudo-random bit sequence and whereindetermining the error rate comprises determining a bit error rate usingthe pseudo-random bit sequence.
 15. The method of claim 11, whereinsweeping the configurable calibration parameter across the subset ofvalues comprises sweeping the configurable calibration parameter throughselected values from the range of valid values for the configurablecalibration parameter until an end condition is reached based on theresults of the testing.
 16. The method of claim 15, wherein the endcondition is reached when an error rate resulting from the testing isbelow or above a threshold error rate.
 17. The method of claim 11,wherein sweeping the configurable calibration parameter across thesubset of values comprises: initializing the configurable calibrationparameter to a first value and then increasing the configurablecalibration parameter until an end condition is reached based on theresults of the testing; and initializing the configurable calibrationparameter to a second value greater than the first value and thendecreasing the configurable calibration parameter until the endcondition is reached.
 18. The method of claim 11, wherein determiningthe set of calibrated values for the configurable calibration parametersbased on the results of the testing comprises determining a centroid ofa multi-dimensional array formed by the results of the testing.
 19. Themethod of claim 11, wherein the receiver comprises an equalizer andwherein at least some of the configurable calibration parameterscomprises equalization parameters.
 20. The method of claim 19, whereinthe equalizer comprises a multi-tap filter and the at least some of theconfigurable calibration parameters comprises weighting values for thetaps of the multi-tap filter.
 21. One or more non-transitory computerreadable mediums storing instructions for a control circuit that, whenexecuted by the control circuit, cause the control circuit to performoperations comprising: determining, for each configurable calibrationparameter of a plurality of configurable calibration parameters for areceiver for processing a received signal from an interconnect coupledto the receiver, a range of valid values for the configurablecalibration parameter; for each configurable calibration parameter:sweeping the configurable calibration parameter across a subset ofvalues from the range of valid values for the configurable calibrationparameter; and testing the received signal from the interconnect foreach value in the subset of values and storing a result of the testingfor the value; and determining a set of calibrated values for theconfigurable calibration parameters based on the results of the testing.